Method of making sorptive getter structure



Aug. 9, 1966 J. s. CULLEN METHOD OF MAKING SORPTIVE GETTER STRUCTURE Filed Oct. 4, 1962 ATTOFNEYQ United States The present invention relates to an improved sorptive getter structure and an improved method of fabrication thereof.

A sorptive getter structure is a device containing a material for use in various types of equipment wherein it is necessary to remove impurities or unwanted constituents from the environment in which said sensitive parts of equipment or located. Generally when a desiccant is used as the active component of the getter, the function of the desiccant is to remove moisture to provide a relatively moisture-free environment for the sensitive parts of the device with which the getter is associated. Such structures are used with electrical components, such as transistors, to control moisture in the atmosphere around the crystals and maintain the stability of the transistor.

In the past, the incorporation of a getter material into electrical components was relatively expensive and inefiicient. In one form of getter a wafer or tablet of the active material was placed within a getter capsule and secured therein by means of a permeable cotton disk which, in turn, was held in place by a metal retaining ring. The foregoing structure was relatively expensive because, in addition to the necessary components or the getter structure, namely, the capsule and the desiccant, the retaining ring and cotton disk were also required. The additional expense of the foregoing types of getter structures were not only due to the requirement for the additional parts, but also due to the labor cost involved in assemblying all of the foregoing parts into a finished article. However, notwithstanding the relatively high cost, the foregoing type of getter structures were relatively inefiicient because the retaining ring would slip or move under physical shock and also the tablet sometimes would break, since not .tig-htly held. It is with the providing of an improved getter structure which is not subject to the foregoing shortcomings of the prior art that the present invention is concerned.

It is accordingly one object of the present invention to provide an improved sorptive getter structure which is relatively economical to produce and highly efiicient in operation.

It is another object of the present invention to provide an improved method of fabricating a sorptive getter structure which permits a highly eflicient getter to be made with -a minimum of parts.

Another object is to provide a getter structure which is adapted to automated production with a simple adaptation of conventional tableting machines.

Other objects and attend-ant advantages of the present invention will readily be perceived hereafter.

The improved getter of the present invention comprises a capsule and a sorptive tablet contained therein, the latter being held in said capsule by a deformed portion of said capsule. The more specific aspects of the improved getter str-ucture can readily be appreciated from the improved method of fabrication thereof. In this respect a capsule of deformable material is provided and granuated sorptive material is inserted therein. The outer surface of the capsule is then held by a die and a punch is brought to bear on the granulated sorptive material within the capsule with sufficient force tocause said granulated sorptive material, which is confined between the capsule wall and the punch, to be formed into a rigid tablet.

In one form of the invention, the die has cut-away portions at least proximate the area in which sorptive material is located. The tableting of the sorptive material by pressure, while confining the sorptive material between the punch and the capsule wall, results in the simultaneous exertion of a force through the sorptive material on the wall of the capsule and thus deforms the capsule from its original shape. When the punch is removed, the wall of the capsule will somewhat tend to spring back to its original shape but will not do so fully. The radially inwardly directed compressive force exerted on the tablet by the foregoing springing back of the capsule and the complementary mating relationship between the outer peripheral portion on the tablet and the deformed portion of the capsule will cause the tablet to be retained securely within the capsule.

In another form of the invention the capsule is of conical form, enlarging toward its mouth, and the sorptive material engaging end of the punch is of slightly smaller external diameter than the internal diameter of the capsule at the exposed face of the tablet and as a result, in tableting the sorptive material, the punch digs into the side of the wall of the capsule and forms an integral inwardly projecting :annular lip from the side wall at the exposed face of the tablet and which forms a positive retaining lip for the capsule.

In addition to placing the sorptive material within the capsule by the use of either of the foregoing methods, the punch which effect the above-described tableting may also be used to deform other portions of the capsule incidental to producing a finished getter of a particular configuration. Because of the fabrication of the improved getter structure by either of the above-described methods, the cost thereof is reduced by the elimination of both extra parts and the labor required to assemble such parts and, in addition, the reliability of the improved getter structure is increase-d by eliminating said extra parts. Furthermore, since the sorptive material is actually pressed into place in the capsule at extremely high force, the possibility that the sorptive material may became dislodged from the capsule is practically non-existent. The present invention will be more fully understood when the following portions of the specification are read in conjunction with the accompanying drawings wherein:

FIG. 1 is a vertical cross sectional view of a punch and die during the initial step of drawing a blank into a cupshaped capsule by means of progressive dies.

FIG. 2 is a similar cross sectional view of the second step of the drawing of the capsule by a second punch and die.

FIG. 3 is a similar cross sectional view of the drawing of the capsule by a third punch and die.

FIG. 4 is a vertical cross sectional view illustrating the practice of one form of the invention and showing the blank of FIG. 3 located in a fourth die and having granular sorptive material therein preparatory to compression by a fourth punch which also deforms a part of the capsule.

FIG. 5 is a similar cross sectional view of the die, punch, capsule and sorptive material of FIG. 4 and showing the punch in its lowermost position wherein it has completed forming the capsule and also has totally compressed the granular sorptive material as well as having deformed the capsule adjacent the sorptive material to retain the tableted sorptive material therein.

FIG. 6 is a similar cross sectional view of the die, punch, capsule and sorptive material of FIGS. 4 and 5, showing the punch being removed from the die of said figures after the sorptive material has been compressed and the capsule has been deformed.

FIG. 7 is a cross sectional view of the improved getter of one form of the present invention removed from the die of FIGS. 4, 5 and 6.

FIG. 8 is a fragmentary view similar to FIG. and illustrating the practice of a modified form of the invention.

During the initial stage of the progressive drawing of a blank into a cup-shaped capsule, a punch 10 is used in cooperation with a die 11 to draw a substantially fiat sheet material blank into the preliminary cup-shaped member 12 shown in FIG. 1. Thereafter a punch 13 is used in conjunction with a die 14 to draw preliminary up-shaped member 12 into intermediate cup-shaped member 12a. Progressively, a punch 16 is used in conjunction with a die 17 to draw intermediate cup-shaped blank 12a into cup-shaped capsule 12b. The material which is used for the capsule may be any suitable metal, such as cold rolled steel plated with copper or precious metals, which is capable of being drawn in the foregoing manner. In addition, any other material which is capable of being distorted to retain tableted material in position can be used.

In the practice of one form of the invention, often the cup-shaped member 12b has been formed to the configuration shown in FIG. 3, it is placed in a die 19 and a pre determined amount of granulated sorptive material 20 is inserted therein. The die 19 is a cut-away portion 21 located therein. The bottom Wall 22 of cup-shaped capsule 12b is supported on the bottom wall 23 of the die 19 and the side wall 24 of cup-shaped capsule 12b is supported by the side wall 25 of the die 19. A punch 26 is brought downwardly into cup-shaped capsule 12b after it has been filled with said predetermined amount of powdered or granular sorptive material 20 and the pressure exerted by die 26 on the material 20 confined within capsule 12b causes it to be compressed and to be formed into a rigid tablet 20a.

Furthermore, from FIG. 5 wherein the punch 26 is in its lowermost position relative to die 19, it can be seen that the compression of granular or powdered sorptive material 20 into the tablet 20a causes the lowermost peripheral portion of the cup-shaped capsule, now designated at 120, to be deformed radially outwardly into a slightly bulged portion 28. The outer peripheral surface 29 of tablet 20a is thus forced by compression into complementary mating relationship with the internal surface 30 of bulged out portion 28. Considering that the sorptive table 20a is now rigid as a result of the compression thereof, the complementary mating relationship 2930 is sufficient to hold tablet 20a retained within capsule 120. From the foregoing description it will be appreciated that the close confining of all portions of capsule 12c within die 19, except in the area 21 of the latter, permits the foregoing action to take place.

From FIGS. 4, 5 and 6 it can also be seen that punch 26 has an upper curved portion 31 which is adapted to mate with upper curved portion 32 of die 19 to deform the upper edge 33 of capsule 12b from the configuration shown in FIG. 4 to the configuration 34 of the capsule 12c shown in FIG. 5. Thus, in addition to performing the tableting function and the expansion of portion 28 of capsule 12c, the punch and die combination 19-26 is also used for deforming the capsule 12b at 34.

From FIG. 6 it can be seen how the punch 26 is withdrawn from the die 19 to leave the capsule 120 in its final form shown in FIG. 7. After punch 26 is withdrawn, to thereby relieve the pressure on tablet 20a, the bowed-out or bulged-out portion 28 of capsule 12c will tend to spring back somewhat to thereby provide a compressive radially inwardly directed force on tablet 20a to thereby enhance the mating engagement between portion 28 of capsule 12c and tablet 200. It will thus be seen that tablet 20a is held within capsule 120 not only by the complementary mating engagement between the outer surface 29 of tablet 20a and the inner surface 30 of capsule 120 but also because of the compressive force exerted radially inwardly by portion 28 of capsule 12c incidental to its tending to spring back to its original condition.

Sorptive materials which can be used to form tablet 20a described above may be barium carbonate, barium oxide, boric acid, metal-alumino silicate and various zeolites. Furthermore, the foregoing sorptive materials will not only change from granular form into a rigid tablet incidental to the compression thereof within a confined chamber in the manner described above, but will also retain their tablet form with a high resistance to fracture. It is to be especially noted that tablets formed from the above materials in the above-described manner will definitely retain their tablet form as a function of the recompression exerted thereon by portion 28 of capsule 12c tending to spring back to its predetermined condition.

In addition to the above-described compounds, other compounds may also be used which have the desired sorptive properties and which will cohere under pressure and retain their tablet form against the recompression exerted by the capsule. While the foregoing description has referred to the sorptive material as being granular, it will be understood that these terms are meant to encompass the insertion of a single pellet into capsule 12b, which pellet may be crushed and reformed by die 26. Furthermore, if desired, any suitable additives or binders may be used with any of the above sorptive materials to vary the properties of such materials for any particular application.

It has been found that a compress-ion ratio of 2 /2 :1 has been effective in tableting the above materials from a granulated state into a rigid tablet form. Furthermore, it has been found that two tons of force applied over an area of .618" can be utilized to provide the abovedescribed results.

In FIG. 8 is illustrated a modified form of the practice of the present invention from which it will be noted that the capsule 40 has a flat end wall 41 and a conical side wall 42 forming a conical cavity 43 which enlarges toward the mouth (not shown) of the capsule. This capsule 40 is shown as contained within a die 44 having a cavity 45 holding the capsule 40 and substantially conforming to the external surface of the capsule. The punch 46 is shown as being of cylindrical form with its working end face 47 being of slightly larger diameter than the internal diameter of the capsule 40 at the exposed face 48 of the tablet 49 of sorptive material.

With the form of the invention shown in FIG. 8 the capsule 40 is first placed in the conforming cavity 45 of the die 44 and a suitable quantity of finely divided or granulated sorptive material is placed in the bottom of the capsule. The punch 46 is then advanced axially into the capsule from its mouth (not shown) to compress the granular sorptive material into the tablet 49. Before fully compressing the tablet the margin of the working surface of the punch 46 engages and shears a lip 50 of material from the conical side wall 42 of the capsule and displaces the sheared material radially inwardly over the face 48 of the tablet to form an integral, inwardly projecting, annular lip from the capsule wall 42 to act as a retainer for the tablet 49.

While preferred embodiments of the present invention have been disclosed, it will readily be understood that the present invention is not to be limited thereto, but may be otherwise embodied within the scope of the following claim.

What is claimed is:

A method of making a getter structure comprising the steps of drawing a blank into a cup-shaped capsule having a wall portion, inserting a sorptive material into said capsule, utilizing a die to hold said capsule and a punch associated with said die simultaneously to deform and shear a circular lip from said wall portion and to compress said sorptive material in said capsule while confining said sorptive material by said wall portion of said capsule to tablet said sorptive material in said deformed wall portion, whereby said punch causes said sorptive material to assume a rigid form and said deforming and 5 lip forming of said wall portion provides interengagement between said tableted sorptive material and said wall portion of said capsule to retain said tableted sorptive material in said capsule.-

References Cited by the Examiner UNITED STATES PATENTS 1,783,927 12/ 1930 Rieke 2951O 1,992,855 2/1935 Bell 29-5 10 2,116,244 5/ 1938 King 206.4

Haller 29421 XR Haggart 29527 Stover 264-268 Fransen 206.4

Meisen 206.4

JOHN F. CAMPBELL, Primary Examiner.

EARLE DRUMMOND, WHITMORE A. WILTZ,

Examiners.

10 R. H. SCHWARTZ, J. C. HOLMAN,

Assistant Examiners. 

